Present day and future Low Earth Orbit (LEO) satellite systems require low cost, high gain antennas for ground stations in order to meet system requirements. Because LEO satellites are moving with respect to a ground station and because of the high gain requirement for the antenna, the antenna needs to track the satellite. In addition, it is desirable for a ground station to track more than one satellite simultaneously in order to achieve a make before break hand-off from one satellite to another.
Conventional mechanical tracking high gain antennas are available that can acquire and track LEO satellites. However, mechanical antennas typically have moving parts, which can introduce reliability issues. In addition, a high profile is required to physically rotate the antenna in order to track the satellite. A high profile is undesirable in many residential installations. Typically, a mechanically pointed antenna can only track one satellite at a time, and this means two antennas have to be used, which compounds the size and reliability issues.
One potential solution to the limitations of a mechanical antenna is a phased array. Array antennas are well known in the art. In array antennas, multiple radiating/receiving elements are used to establish one or more beams. Phased array antennas have directional beams that can be steered in two different directions, typically azimuth and elevation.
Phased array antennas are constructed using multiple antenna elements, multiple phase shifters connected to the multiple antenna elements, and a distribution network connected to the phase shifters. In some applications, the phase shifters are the most critical components in an array antenna system. The phase shifter is required to produce a controllable amount of phase shift over the operating frequency band for the phased array antenna system.
Phase shifters have been constructed using a variety of techniques including ferrite materials and pin diode switches. Current methods for implementing phased shifters for phased array antennas are expensive and complex.
Accordingly, a need exists to provide a number of independently controllable phase shifters in a low cost phased array antenna that is functional at microwave and/or millimeter wave frequencies.
In particular, there is a significant need for a low cost single phased array antenna comprising a number of independently controllable phase shifters having sufficient phase range to allow the antenna to be steered over a wide field of view.